Defining meaningful postoperative change in epilepsy surgery patients: measuring the unmeasurable?

Two hundred and ninety epilepsy surgery patients completed the Hospital Anxiety and Depression Scale and were assessed on a list learning task preoperatively and 1 year postoperatively. Deterioration and improvement in verbal memory were determined using reliable change indices (RCIs) at 80 and 90% confidence limits. Almost one third of patients (27%) experienced a deterioration in verbal learning. The number of left temporal lobectomy patients who had deteriorated outnumbered the right temporal lobectomy patients by 2:1. Significant improvements in verbal learning were seen in 21% of the right temporal lobectomy group and 10% of the left temporal lobectomy group. Patients who were seizure-free postoperatively were not more likely to experience a postoperative deterioration or improvement in memory than those who continued to experience seizures. No significant relationships were found between subjective ratings of postoperative memory function and objective indices of change. Reliable, objective indices of postoperative deterioration in memory function may bear little relation to the patient's subjective experience. This should be considered when statistical predictions are used as the basis of preoperative counseling.